How do you perform unit test on a Salesforce trigger?

Hi,

Unit tests are class methods that verify whether a particular piece of code is working properly. Unit test methods take no arguments, commit no data to the database, send no emails, and are flagged with the testMethod keyword or the @isTest annotation in the method definition. Also, test methods must be defined in test classes, that is, classes annotated with @isTest.

For example:

@isTest
private class myClass {
static testMethod void myTest() {
// code_block
}
}

Thanks